Beam phasing method and apparatus for adjusting a timing of beam projections

A method for adjusting the timing of beam projections in a beam detector. The method includes projecting a beam for the purpose of detecting obscuration of the beam and, if a level of signal of the beam detected is less than a threshold for each of a number of consecutive projections or for each consecutive projection over a pre-determined time period, initiating a warning, signalling an alarm or otherwise reacting. The method further includes adjusting the timing of projecting the beam from a nominal transmit interval ‘T’ to be within a window time-period ‘W’ extending from an amount before to an amount after the nominal transmit interval ‘T’.